Electric switch



Sept. 14, 1954 c. F. PULVARI ELECTRIC SWITCH 2 Sheets-Sheetl 1 Filed Oct. 31, 1951 lNvENToR UharZesZZPuZz/ap BY MMM afm ATroRNEYs Sept. 14, 1954- c. F. PULVARI 2,689,283

- ELECTRIC SWITCH Filed oct. 31, 1951 2 SlneetSJSheet 2 fag f3] Il? ./39 Jil IH l IIIIHIIIIII o O,

Patented Sept. 14, 1954 ELECTRIC SWITCH Charles F. Pulvari, Washington, D. C., assignor to Aerovox Corporation, a corporation of Massachusetts Application October 31, 1951, Serial No. 254,051

9 Claims.

This invention relates to electric switches, more particularly of the thermally controlled snap actiontype.

It is among the objects of the invention to provide an inexpensive switch of the above type that is light in weight, compact, yet rugged and durable, that has but few parts which may readily be assembled by mass production methods and do not require critical adjustment, which switch is not likely to become deranged even with long continued use and will operate dependably, automatically to'effect opening and closing of a circuit at a predetermined frequency Without likelihood of arcing between its contacts.

Another object is to provide a switch of the above type which utilizes a'high resistance conduit or wire as the control element and which will retain such conduit or wire under a minimum of strain so that. it will not stretch even after long periods of time, thereby ensuring dependable operation.

Another object is to provide a circuit incorporating a switch of the above type and having a pair of signal lamps associated therewith as well as a pilot lamp, said lamps being so correlated that in the event one or more of the signal lamps should burn out the pilot lamp will so indicate.

According to the invention the switch comprises a resilient switching unit comprising a contact carrying arm xed at oneend and movable between two extreme positions, to bring a contact on said arm into and out of engagement with an associated rlxed contact at one or the other of said extreme positions. The switch is constructed and arranged for normal biasing of said contact carrying arm to one of said extreme positions and has an intermediate position of unstable equilibrium for said contact arm between said two positions, from which, upon application of tension thereto, the contact will snap to the other extreme position so that upon movement of such movable contact into and out of engagement with the fixed contact, arcing will be avoided. The contact arm is controlled by a heat extensible conduit or wire operatively connected thereto and upon cooling and contraction of said wire will move from its normally biased position past said position of unstable equilibrium so that the snapping movement of the contact on such arm will be eiiected. The switch is so designed that when, for example, the contact arm has moved to its normally biased position upon expansion of said wire by flow'of current therethrough, the Wire will be short circuited with resultant reduction of such current flow and cooling and contraction of the wire and resultant movement of the movable contact past the position of unstable equilibrium to'eiect snapping movement of such contact to the other extreme position. Such movement of the contact will remove the short circuit about the wire with resultant heating and expansion thereof and movement of the contact arm past the position of unstable equilibrium to effect snapping of the contact thereon back to the rst extreme position.

In the circuit hereinafter described, to illustrate the invention, the switch is connected to a pair of parallel connected signal lamps in such manner that when the wire is short circuited the lamps will become incandescent and when the short circuit is removed the lamps will be out.

In a preferred embodiment of the invention, the switch desirably includes a second contact carrying arm connected in series with the parallel connected lamps, a source of current and the rst contact carrying arm and is also controlled by a heat extensible wire of less resistance than said rst heat extensible wire. The second heat extensible wire when contracted, due to insufiicient current flow therethrough normally is spaced from a xed contact which may be connected in series with an electric device such as a pilot lamp and upon expansion of said second heat expansible wire and movement of the contact carrying arm into engagement with the xed contact, the pilot lamp Will be connected in parallel'with said signal lamps to turn on and oi in synchronization therewith. If one or more of the signal lamps should be defective, insuilicient current will flow through the second heat extensible wire to retain the contact arm against the fixed contact andthe pilot lamp will not be illuminated.

In the accompanying drawings in which are shown one or more of various possible embodiments of the invention,

Fig. 1 is a longitudinal View of an electric switch partly in cross section,

Fig. 2 is a longitudinal sectional view taken along line 2-2 of Fig. l,

Fig. 3 is a transverse sectional View taken along line 3-3 of Fig. 1,

Fig. 4 is a perspective view of the switch assembly,

Fig. 5 is a side elevational View of the contact arm and switch arm,

Fig. 6 is a circuit diagram incorporating the switch of Figs. 1 to 5,

Fig. 7 is a front elevational View of another embodiment of the switch,

Fig. 8 is a detail perspective view of a portion of the switch shown in Fig. '7,

Fig. 9 4is a longitudinal View partly in cross section of another embodiment,

Fig. l is a view similar to Fig. 9 of still another embodiment of the switch, and

Fig. 11 is a longitudinal sectional view taken along line II-II of Fig. 10.

Referring now to the drawings, the switch shown in Figs. 1 to 6 inclusive, desirably comprises a supporting post I I preferably of conducting material having a laterally extending member I2 at one end thereof with depending ears I3 which may be passed through corresponding openings in an insulating disc I4 and bent over, securely to mount the post on the disc.

The post I I desirably has a laterally extending wing I6 preferably formed integral therewith at one edge thereof adjacent the disc I4. Affixed t0 `wing I6 as by welding, is the lower end of a switch assembly which is of resilient sheet metal, prefer--4 ably spring steel. As shown in Fig. fl, the switch assembly includes a Contact arm I1 which is de-y sirably substantially rectangular and of greater length than width having its central portion cut away to denne a switch arm I8 integral therewith and desirably stressed so that it is normally urged to the left as shown in Fig. with respect to contact arm I1. The switch arm I8 is of reduced Width as at 2I near its free end 22 which is spaced from the cross piece 23 of the contact arm which carries a contact 32.

Associated with switch arm IB is a high resistance conduit 26, preferably of Nichrome wire, one end of which is alixed as by soldering to an outwardly extending finger 21, desirably formed integral with the switch arm I8 at the free end thereof. The other end of the wire 26 is affixed to an insulating bead 28 desirably mounted on an arm 29 extending laterally outward from mem-v ber I2 and is connected to a terminal 3| mounted on disc I4.

The wire 26 when cold is of such length as to pull and retain the switch arm llik well to the right of contact arm I1 as shown in Fig. 1. By reason of the stress or. tension of such switch arm I8A when pulled to the right as shown in Fig. 1, wire 26 would normally be under considerable strain. To. reduce s uch strain and also to impart a togglelike snap action movement to the Contact arm I1 for movement 0f' contact 3.2. int@ and 011i 0f engagement with spaced .Siep 33 and geniet, 34 positioned on each side of contact 32 respectively, a'bowefd leaf spring 35 is provided, preferably of` resilient spring steel normally under tension and tending to" straighten out. The spring 35 as shown"y in`Figs'. 2` ande, is so positioned that the` fingers 36 at one end thereof will rest on shoulders 24 laterally of thev reduced end 2I of the switch arm I1 and the fingers 36 at the other end thereof will rest in notches 33 formed in the inner edge of the cross piece 23 at the end of the contact arm I1.

The spring 35 normally will exert tensionA in opposed directions against the cross arm 2-3 of contact'arm I1 and against the switch arm I8 so that when the shoulder portion 24 of the switch arin is to the'left of the contact arm, the crossarm of the latter will be retained in the extreme position to the right against contact 34 Aand when the shoulder portion 24 is to the right ofthe contact arm the cross arm of the latter will be retained in the other extreme position to the. left against stop.. 33..k When the shoulder portion 24 lies in the same plane as the contact arm. the latter will be in an intermediate position of unstable equilibrium for the spring member will urge the cr'ss piece 23 neither to the left nor to the right and any slight movement of the shoulder portion 24 beyond such intermediate position in either direction will effect a snapping action of the cross piece in the opposite direction to the corresponding extreme position.

As the tension of switch arm I8 is desirably greater than that of spring 35, the arm IB will tend tp move to the position shown in Fig. 5. However, such movement is restrained by the wire 26, which, when cold, retains the switch arm |13 in the position shown in Fig. 1, with contact 32 on contact arm I1 in engagement with stop 33. Desirably, the stop. 33 is a laterally extending finger formed integral with post I I near the upper end thereof and positioned on one side of contact 32 and the fixed contact 3 4 is mounted on post I I and insulated therefrom. To this end the oo ntact 34 desirably is an angle bar with a mounting portion 4I ailixed to the upper end ofV the post I I4 as by a rivet 42, insulating means I3v dsirably intervening between mounting portion 4I and the post I I. A lead 44 aflixed to a lug 45 integral with portion 4I connects' Contact 34 to terminal 3| mounted on disc I4.

A second heat responsive switch is also desirably mQmted. 0n.. P951? U A5 Shown m Figs- 1 an@ 3 Such SWQh delmply ompries arm 4,8 Pref? erably of resilient serine Sisal, ailles@ et @es end as by welding to Wine I6, @elevate Wins 6.- Arm. 48, which carries a contact 5I, is bent outwardly at its extremity 52 to whihis arlixed, as by soldering, one end of a high resistance wire y53, de :siiallllif'v of greater thickness and less resistance than wire. 26. The other end of wire 53 is desirably afxed in an insulating bead 54 mounted on an` arm 55 extending laterally outward from member I2 and is connected to a terminal 56 mauntedkon discV Il,

Associated with contact 5I is a fixed Contact 51 which is desirably a finger extending parallel tov the plane of arm 43. Contact 51 may be an angle bar, one face of which is a mounting portion53` afiixed to post II as by the rivet 42 and insulated from the post and from contact 34 by meansof. insulators 43, said mounting portion 58 having an integral lug 6I which is connected by'lead. $2 to a terminal 53. on the disc I4.

The spring arm 48 is so stressed that itgwould normally move the contact 5I thereof into enf. gagernent with fixed contact 51. However, the

wire 53 associated with arm 48 is ofy such normal length when cold as to retain the contact 5I spaced fromnxed contact 51 and when the wire elongates due to now. of current therethrough, it will do so suiciently to permit contact 5I to move into engagementwith fixed contact 51.

Desirably., means are provided to limit the outward movement of arms I-and 48 under urging of the associated wires 26- and 63 when cold. To this end a limiting member 65 maybe aiiixed tol post Il by rivet 4gv and disputed therefrom and has lateral arms4 61, each with anvend finger 63 extending at right angles thereto, one of said fingers being interposed between arm 48 and wire 53 and the other-'in the path of move-A ment of the free end 212V of arm I8 under the urging *ofcold and contracted wire 2B. l(

The entire unit is desirably enclosed inea suitable tubularcasing 69 axed in any` conventionalmarinierV as at 1I to theudisc I4. Desirably the dise. I4. also has a'braclret'A 12 affixed thereto to afrnrd-` ready-'mount of the unitA in any-suitableJ placeas, for4 example, in an automobile inwhlch the unit is to be used.

Although the device heretofore described may be used in many different types of installations, the example herein described is the control for the turning signal lamps of an automobile. One pair of lamps and 16, preferably connected in parallel, as shown in Fig. 6, and at one side of the automobile front and rear, is controlled by means of a switch 11 which may be mounted, for example, on the dashboard of such automobile. One side of the parallel connected lamps is connected by lead 18 to one main M-I as for instance the battery of the car. The other main M-2 is connected through switch.11 to the terminal 3| of the device and the other side of the pair of parallel connected lamps is connected by lead 19 to the terminal 56 of the device.

In the event that one or more of such lamps 15, 16 should be defective, it is desirable to provide a signal which will indicate this condition toV the driver of the car. To this end a pilot lamp 8| may be mounted on the dashboard of the car. One side of the pilot lamp 8| is connected by lead A82 to the terminal 63 of the device and the other side of the pilot lamp is desirably connected by lead 83 to the parallel connected lamps 15, 16 as at 84.

To indicate a turn the driver closes switch 11 on the dashboard of the automobile. As a result, a circuit will be completed from the power main M-2, switch 11, terminal 3l, high resistance wire 26, switch arm I8, contact arm I1, through the metal post contact arm 48, high resistance wire 53, terminal 56, lead 19 through parallel connected lamps 15 and 16 and lead 18 to the power main M-I.

By reason of the high resistance of wire 26 and wire 53 in series therewith, the voltage drop across the parallel connected lamps 15 and 16 will be insufficient to effect illumination thereof. As the pilot lamp 8| is connected to the contact 51, which is not yet engaged by the contact arm 48, the lamp 8| will also not be illuminated.

With the ow of current through wires 26 and 53, they will heat up and elongate. The elongation of wire 26 will permit the tensed switch arm I8 to move to the left as shown in Fig. l against the tension of the spring member 35. As such spring member 35 is exerting tension against spring arm I8, the resultant tension applied to the wire 26 will be the difference between the tensions of spring arm I8 and spring member 35. These tensions are initially adjusted so that the tension of spring arm I8 will be only slightly greater than that of spring member 35, thereby retaining the relatively thin wire 26 under but slight tension.

With continued elongation of wire 26 with passage of current therethrough, the shoulder portion 24 of spring arm I8 engaged by spring member 35 will move in the direction of the arrow shown in Fig. 1 into the same plane as the contact arm or the position of unstable equilibrium. Up to and including this position the contact 32 carried by cross piece 23 of the contact arm will be retained to the left against stop 33. Further elongation of wire 26 will permit the shoulder portion 24 of the spring arm I8 tokmove slightly past the plane of the contact arm at which time the spring member 35 will snap the cross piece 23 in a toggle like action to the right so that contact 32 will quickly engage contact 34.

Inasmuch as the spring member 35 will retain the contact 32 against stop 33, until the switch arm |8 moves past the plane of the contact arm, there will be substantially no movement of the contact 32 away from stop 33 until such snap` actionv occurs. In addition, current flow through wire 53 will cause it to heat up and become elongated so that the free end of the arm 48 will gradually move to the right for engagement of contacts 5I and 51.

The resultant circuit due to the movement above described of contact 32 into engagement with contact 34 will effect a short circuiting of wire 26. Thus the circuit will be from main M-2, switch 11, terminal 3|, lead 44 to contact 34, contact 32, contact arm I1 through post II. arm 48, wire 53, terminal 56, lead 19 through the parallel connected lamps 15 and 16, and lead 18 to the other power main M-I.

By reason of the short-circuiting of the high resistance wire 26, the Voltage drop across lamps 15 and 16 will be increased sunlciently to cause them to light. In addition, as contacts 5| and 51 are also in engagement, the pilot lamp 8| will be connected in parallel with lamps 15 and 16 so that it will also light. The circuit for the pilot lamp 8| is from main M-2, switch 11, terminal 3l, lead 44, contacts 34 and 32, contact arm I1, post arm 48, contacts 51 and 5|, lead 62, terminal 63, lead 82 to one side of the lamp 8l and from the other side of the lamp through lead 83 to the other power main M-I.

Wire 28, being short circuited, will cool and contract, which will cause the free end 22 of the switch arm` I8 to move to the right to the position shown in Fig. l, thereby also moving to the right, the end of the spring member 35 engaging the shoulders 24 of switch arm I8. When such end of the spring member 35 moves past the plane of the contact arm I1, the pressure of the spring member will be exerted against the cross piece of the contact arm in opposed direction to effect a togglelike action thereby to snap the contact carrying end of the latter, which had been until this time retained against contact 34, to the left, quickly to disengage contacts 32 and 34 without likelihood of arcing therebetween and moving contact 32 into engagement with stop 33. The above cycle of operation continues as long as switch 11 remains closed.

As a result of the disengagement of the contacts 32 and 34, the wire 26 will again bein series with the source of current and the parallel connected lamps. Consequently, the voltage drop across such lamps will be reduced as will the voltage drop across the pilot lamp 8| and the lamps will be extinguished. As current will ilow through the wire 53 regardless of the position of contact arm I1, the wire 53 will remain in elongated condition and contacts 5| and 51 will remain in engagement so that the pilot lamp 8| will be retained in parallel with lamps 'I5 and 16 to be turned on and off in synchronization with such lamps.

In the event that one of the lamps, 15, 16, i. e., lamp 15 should be broken, the current ilow through the circuit will be correspondingly decreased and as a result the current flow through the wire 53 will not heat such wire for sufficient elongation to retain the contacts 5I and 51 in engagement. Under the resultant cooling and contraction of wire 53 the contacts 5I and 51 will separate, breaking the circuit from the source of power to the pilot lamp and though the good lamp 'I6 will still function and turn on and oil, the pilot lamp 8| will not and the driver of the automobile is advised that one of his signal lamps is not operating.

As the switch arm 48 does not move repeatedly during operation of the switch as does contact 7. armV l1, although contacts and 51 will move apart slowly in the event one of thesisnal lamps is defective, and arcing may occur, such arcing is` relatively `infrequent and hence no objectionable pitting of contacts 5| and 51 will result.

The embodiment of the switch shown in Fiss. '7 and desir-ably comprisesa base 9| of insulating material having a supporting post 92 affixed thereto. The supporting post which also desirably is of insulating material, is substantially U- shaped. having its cross piece 93 extending at right angles to the base andhaving its legs 94 and 95 extending longitudinally of the base and parallel thereto, thev leg 94 Adesirably being suitably aiiixed to said base. Affixed at one end tothe cross piece 93., which is desirably recessed as at 96,;ls a contact arm 91 of resilient material such as; spring steel normally biased so as to have its free. end move to the left, as shown in Fig. 7, so thatthe contact 90 at the free end of the contact arm, may engage a xed contact 99 securely affixedto the frame by means of a bracket |0| and is spaced' from a contact |00` affixed to base 9|. Arm 91y desirably has a cross bar |02 at the free end thereof with dependingy switch arms |03 and |04 at each end thereof respectively, said switch arms also being of resilient material such as spring steel and bowed, as shown at |05, with the free ends of said switch arms being seated in notches |06 respectively in the upper ends of legs 941and95.

With-the construction and arrangement of contact arm 91, switch arms |03- and |04 and mount 92. above described, when the lower portion of the contact arm adjacent the iixed end thereof is tothe left of said notches, the contact 90 will be retained'by the bowedswitcharms in the extreme position tothe left against contact 99. When such4 lower portion` of contact arm 91 is to the right of notches |06, the contact 99 will be retained in the other extreme position, i. e., to the right against; stop |00'. When such lower portion of the contact armv 91 lies inthe same plane as the notches |06, the contact arm will be in an intermediate position of unstable equilibrium and with any slight movement of such lower portion of the contact arm beyond such intermediate position in either direction the contact carrying end 900i the contact arm will be snappedto the corresponding extreme position;

Associated with the contact arm 91and controlling the latter is a high resistance wire one end oi which is aixed as by soldering tothecontact arm 91 between its mounted end and the pivot points |06of the switch arms |03 and |04. The wire which extends outwardly from the contactr arm 91 has its free endafnxed to one of the legs ||2 of a supporting bracket ||3 which desirably is substantially Ll-shaped asshownand.

has an opening ||4 in the other leg H5 thereof through which the wire extends, the bracket ||3 being connected to contact 99 byv means of a lead H0.

To install the devceabove-described, the bracket |3 is connected by lead I2 to one side of parallel connected turning signal lamps |22 and |23 which may be` installed, for example, in conventionalmanner at one side oithe front and rear of` an automobile. The other side of said lamps |22, |2-3 isconnected by lead |24 to switch4 |25, desirably on the dashboard of the automobile, and from the switch to main M-I of a source of power, the other main M-2 of the source of power being connected by lead |2|l.to arm` 91.

When the switch |25 is in normal open position, the high resistance wire will be contracted so that the contact 98l on arm 91 will be engaging stop |00 affixed to the base. When switch |25. is closed to signal a turn, current will flow frommainM-I, switch |25, lead |24 through parallel. lamps |22 and |123, lead |2|, high resist ance wire contact arm 91, lead |20 to main M-2. By reason of the voltage drop across the wire. there will be insufficient voltage across lamps |22 and |23 to illuminate the latter. As wire |v heats upland elongates with flow of current therethrough, contact arm 91 which is normally tensed to the position shownV in Fig. '1, will or to the left ofthe pivot point |00 of the Switchv arms |03, |04. At this time a. toggle-like snap action will occur whichwill quickly move the contact 98 away fromA stopA |00 and into engagement with contact 99. Consequently the high resistance wire will' be short circuited, the circuit being from power main M-|, closed switch |20, lead |24 through parallel lampsy |22 and |23, leads |2| and ||6, through contacts 99'` and 99, contact arm 91, lead |26 to main M-2.

As a result of such connection, substantially the only resistance in the circuit `will be that of the lamps |22, |23 and the voltage drop thereacross will be sufficient to effect illumination.

thereof.

The short circuited high resistance wire will then cool, thereby exerting tension on theV fixed contact 99, such contacts will be retained in4v engagement. When the contracting wireA has moved the'lowerend of the contact arm 91-tot'he right oi the pivot points |06 of the switch armsi |03 and |04, a snap action will be impartedV toA contact arm 91 quickly to disengage contacts 98 and 99 without likelihood of arcing therebetween and to move contact 98 again into engagement with stop |00. The above cycle of operation will'.

continue as long as switch |25 remains closed.

The embodimentv shown in. Fig. 9 desirably comprises a supporting post |3| of` conducting material aixedat its base |30 as by rivet |32 to an insulating disc |33. The upper end of the supporting post, which is offset as at |34, is reversely bent as at |35-todene a pivot arm |36, which is desirably resilient and tensed so thatits free end will normally be urged away from theupost |3|. Afiixed to the upper end o! post |3| as by rivets |31 isa contact arm |30of resilient materialsuch as spring steel; extendingssubstantially parallel to the post |3| andfhaving acontact |39 atitsllower end. Associated with-contact arm |38 is` a switch` arm |4| also of resilient material'bowed as at |42 andaffixed at one end tothe contact carrying end of arm |38, the free-endet said switch arm |4| heilig pivotally mounted in a seat |43 at the freeA sistance wire |45, the other end of saidwire being` aixed in an insulating bead |46 carried on a supporting arm |41, preferably formed integral with the base |30 of the post, the tension on said wire |45 being adjustable by bending arm |41. Desirably, the base |30 carries a pair of contacts and |52 which are insulated from each other and from the base |30 and which are positioned respectively on each side of contact |39 on contact arm |38. Contact |5| is desirably connected by lead |53 to a terminal |54 mounted on insulat- -ing disc |33 and contact |52 and high resistance wire |45 are desirably connected by leads |55 and |56 respectively, to a terminal |51 mounted on said disc |33, the entire unit being housed in a casing |60.

With the construction and arrangement of contact arm |38, switch arm |4| and pivot arm |36, when the pivoted end of switch arm |4| is to the left of contact arm |38, the contact |39 will be retained in the extreme position to the right by bowed switch arm |4| against contact |52. When the pivoted end of switch arm |4| is to the right of contact arm |38, the contact |39 will be retained in the other extreme position to the left against contact |5|. switch arm |4| lies in the same plane as contact arm |38, the contact arm will be in an intermediate position of unstable equilibrium and any slight movement of the pivoted end of the'switch arm beyond such intermediate position in either direction will effect a snapping action of the contact |39 to one or the other extreme positions. To install the device shown in Fig. 9 in an automobile, for example, the terminal |51 is connected by lead |6| to one side of parallel connected turning signal lamps |62 and |63 which are mounted in conventional manner at one side of the front and rear of the automobile. The other side of the lamps is connected to a switch |64 desirably on the dashboard of the automobile and thence to power main M-2. The other power main M-l is desirably connected by lead |65 to rivet |32 to complete the circuit.

In the operation of the device shown in Fig. 9, with contact |39 engaging contact |5|, when the switch |64 is closed, current will now from main M-I through lead |65, rivet |32, post |3|, pivot arm |36, lever |44, high resistance wire |45,'lead |56, terminal |51, lead |6|, through parallel lamps |62, |63, switch |64 to main M-2. By reason of the voltage drop across the high resistance wire |45, there will be insufficient voltage drop across the lamps to light the same. As the Wire 45 heats up andelongates with passage When the pivoted end of' of current therethrough, the tension on lever Y |44 will be relieved and pivot arm |36 will move outwardly from post 3| to its normal position shown in Fig. 9. By reason of the bowed switch arm |4|, the 'contacts |39 and |5| will be retained in engagement until the pivotal seat |43 of the switch arm moves to the left of the plane of the contact arm |38 at which time the contact |39 at the end of arm |38 will snap out of engagement with contact |5| and into engagement Y with contact 52.

With contacts |39 and |52 in engagement as shown in Fig. 9, the high resistance wire |45 will be short circuited. This circuit will be from main M-I, lead |65, rivet |32, post |3|, contact'arm |36, contacts |39 and |52, lead |55 to terminal |51, through Vlead |6I, lamps |62, |63 and closed switch |64 to main M-2. As substantially the only resistance in circuit will be that of the lamps, they will light. v

Since it is short circuited, the high resistance wire |45 will cool and contract with increased tension on lever |44. This will tend to move the lower end |43 of the pivot arm |36 to the right of the position shown in Fig. 9, past the plane of the contact arm |38, When this occurs the switch arm |4| will effect a toggle-like snapping movement of the contact arm |38 o luicklyl to move contact |39 thereon out of engagement with fixed contact |52 without likelihood of arcing between such contacts and into engagement with contact |5| thereby again to place the high resistance wire |45 in series with the lamps |62 and |63.

In the embodiment shown in Figs. 10 and 11, an upright post |1| of insulating material is desirably mounted on an insulating disc |12. Post |1| carries a length of resilient sheet metal, preferably oi' Nichrome which desirably is stamped to denne heat responsive portions |13 and tongues or contact arms |14, |14', the adjacent inner ends of contact arms 14, |14 being afxed to insulating post 1| by rivets |15. As shown in Fig. 11, the heat responsive portions |13 are relatively high resistance thin strips or conduits on each side respectivey, of the contact arms 14, |14', which are relatively Wide and of low resistance. The contact arms |14, |14 are desirably bowed, as shown, and each carries a contact |16, |11 at substantially its mid portion, normally engaging contacts |10 and |19 mounted on and insulated from post 1| and spaced respectively from Xed contacts |18 and |19 electrically `connected by strip |82 and mounted on an insulating post |8| aiilxed to disc |12.

Desirably the rivets |15 associated with contact arm |14' are connected by strip |34 and lead |85 to a terminal |86 on disc |12 and the rivets |15 associated with contact arm |14 are connected by strip |81 and lead |88 to terminal |89 on disc |12.

With the construction and arrangement of `contact arms |14, |14 and strips |13, when the 'portions of the strips |13 adjacent the xed ends of arms |14, |14 are to the right of said arms, the contactsr |16, |11 will be retained in the eX- treme position to the right against fixed contacts |10, |10'. When such portions of strips |13 are to the left of the xed ends of arms |14, |14', the contacts will be retained in the other extreme positions to the left against Xed contacts |18, |19. When the strips and the fixed ends of contact arms |14, |14 are in the same plane, the contact arms will be in an intermediate position of unstable equilibrium and any slight movement of said strips beyond such intermediate position will effect a snapping action of the contacts |16, |11, to one or the other extreme position.

The device shown in Figs. 10 and 11 when used, for example, to control the parallel connected turning signal lamps |9I, |92 on one side of an automobile, has its terminal |86 connected by lead |93 to one side of the parallel connected lamps and the other side of the lamps is connected to a switch |94 desirably on the dashboard of the automobile and thence to power main M-l the other power main lvl-2 being connected by lead |95 to terminal |89.

In the operation of the device shown in Figs. 10 and 11, when no current ilows through the high resistance strips |13, they will be contracted so that, as shown in Fig. 10 they will lie in a plane slightly to the right of the plane of the a'djacent inner ends of the bowed contact arms |14 and |14. In this position the contacts |16, |11 on the contact arms will be spaced from con- 11 tacts |18 and |19 and in engagement with contacts and |10' on post |1|.

When switch |94 is closed, a circuit will be completed from the power main M-l through switch |94, lamps |9\|, |92 and lead |93 to terminal |88, thence through lead |85. strip |84, rivet |15, bowed contact arm |14', high resistance strip |13, bowed contact arm |14, rivet |15, strip |81, lead v|88 to terminal |89 and thence by lead |95 to main M-Z.

As the lamps are in series with the high resistance strip |13, the voltage drops across the lamps will be insufficient to light the same. As current flows through high resistance strips |13, the latter will heat and elongate causing the ends thereof to move in the direction indicated by the arrows. During the initial portion of such movement the contacts |16, |11 on bowed contact arms |14, |14 will remain in engagement with their .associated contacts |18 and |18. As the high `resistance strips |13 continue to elongate, the outer ends thereof will move to the left of the plane of the adjacent inner ends of the bowed contact arms. When this occurs, a toggle-like action will occur to snap the bowed contact arms to the left, thereby moving the contacts |16, |11 .thereon into engagement with contacts |18 and |19 on post |8|. Consequently the high resistance strips |13 -will be effectively short circuited as substantially all the current will ilow through the strip |82 connecting contacts |18 and |19 and the lamps will light as they will be substantially the only resistance in circuit.

Due to such short circuiting of high resistancestrips 13, vthe latter will cool and contract causing the outer ends thereof to move to the right. When the outer ends of the high resistance strips move to the right of the adjacent inner ends of the bowed contact arms, the latter will snap to the right .thereby quickly disengaging' contacts |16 and |11 from contacts |18 and |19 without likelihood of arcing therebetween and moving such contacts `|1| and |11 into engagement with contacts |19 and |10 so that the high resistance strips |13 are again in circuit with resultant turning ofi of the lamps.

With the constructions above described, the movable contacts will not be displaced until the switchingv period and such switching period will occupy but a short interval of time. As a result, there is no likelihood of arcing of the Vcontacts as they are moved away from each other and in addition no critical adjustment of the parts is required for the snap action has a throw of sufncient distance to take care of mechanical variations in manufacture.

It is of course to be understood that in each of the embodiments herein an identical device would be used to control the turning signal lamps on the other side of the front and rear of the automobile and the control switch would be of the single pole double throw type. In addition,

. if desired a pilot light and control therefor similar to that shown in Figs. 1 to 6 could be provided in the other embodiments herein.

As many changes could be made in the above construction, and many apparently widely different embodiments of this invention could` be made without departing from the scope of the claims, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having V-tlfrus described my invention, what I Cil claim as new and desire to secure by Letters Patent of the United States is:

l. An intermittent switch comprising a contact carrying arm iixed at one end, having a contact at the other end and movable at the contact carrying end between two extreme positions, a exible switch arm having one end vfixed with respect to the fixed end of the contact carrying arm and having its other end movable in the plane of movement of the contact carrying arm, resilient means operatively connected to both said flexible switch arm and said contact arm and reacting against both of said arms, said resilient means normally urging said contact arm to one of said extreme positions and providing an intermediate position of unstable equilibrium for said contact arm between said two extreme positions from which, upon application of tension to the movable end of said switch arm` and change of relative position of both said resilient means and switch arm with respect to said contact arm, the contact on the contact arm` will snap over to the other extreme position, and a heat extensible wire connected at one end to the movable end of the switch arm and fixed at the other end to apply tension to said switch arm to move the latter upon cooling and contraction of said wire, from its normally biased position to that of unstable equilibrium for snapping of said contact by said resilient means to the other eXtreme position, whereby upon extension of said wire upon heating thereof, said switch arm will change its relative position with respect to said resilient means and said contact arm, and again cause the contact arm to pass the position of unstable equilibrium so that said resilient means will effect snapping of said contact back. to the first extreme position, said contact when in one extreme position closing a circuit to short circuit said heat extensible wire, said circuit being open when said contact is in theother extreme position.

2. An intermittent switch comprising a contact carrying arm xed at one end, havinga contact at the other and movable at the contact carrying end between two extreme positions, a resilient switch arm having one end xed with respect to the fixed end of said contact arm and having its other end movable in substantially the same plane of movement as said contact arm, said switch arm extending longitudinally of said contact arm .and being normally tensed so that its free end will tend to move away from said contact arm on one side thereof, resilient means coacting with the` free ends of said contact arm and said switch arm to urge said ends in opposed directions when the free end of said switch arm is spaced from said contact arm on either side thereof thereby to bias said contact arm to one or the other of said extreme positions, said switch arm, said contact arm and said resilient means affording a position of unstable equilibrium when said switch arm and said contact arm are in the same plane, a heat extensible wire xed at one end to said switch arm to draw the same upon cooling and contraction of said wire from its normally biased position to that of unstable equilibrium for snapping of said contact by said resilient means to the other extreme position, whereby upon expansion of said wire upon heating thereof, said switch arm will be released and when the position oi unstable equilibrium has been passed by said arm, said resilient means will then snap said contact back to the position of normal bias, said contact when in one extreme position closing a circuit to short circuit said wire, said circuit being open when said contact is in the other extreme position.

3. The combination set forth in claim 1 in which said resilient means comprises a compressed bowed spring member between the contact carrying end of said contact arm and the free end of said switch arm.

4. The combination set forth in claim 1 in which said contact arm is a strip of resilient spring metal and said switch arm is stamped from said strip with one end of said switch arm being integral with that of said contact arm and said resilient means comprises a bowed spring member compressed between the contact carrying end of said contact arm and the free end of said switch arm, the tension of said switch arm being greater than that of said bowed spring member.

5. The combination set forth in claim 1 in which a second contact carrying arm is provided of resilient material, a fixed contact, a second heat extensible wire of less ohmic value than said first heat extensible wire normally retains said second contact arm spaced from said fixed contact, circuit means connects said two contact arms in series and terminals are connected respectively to said first heat extensible wire, said second heat extensible wire and said fixed contact.

6. An intermittent switch comprising a iixed contact, a mount, a contact carrying arm of resilient material having a contact at one end thereof and fixed at its other end on said mount, a resilient spring arm xed at one end to the contact carrying end of said contact arm and extending substantially lengthwise thereof and pivoted at its other end on said mount, said contact arm being biased, normally to urge the contact thereon into engagement with said fixed contact, said contact arm, said mount and said spring arm being constructed and arranged to afford a position of unstable equilibrium when the contact arm and the spring arm are in the same plane, a heat extensible wire fixed at one end to said contact arm to draw the latter upon cooling and contraction thereof from said normal position past said position of unstable equilibrium for snapping of said contact by said spring arm away from said fixed contact, whereby upon expansion of said wire upon heating thereof said contact arm will be released and when the position of unstable equilibrium has been passed by said Contact arm, said spring arm will then snap said contact back into engagement with said fixed contact, said Contact when engaging said fixed contact closing a circuit to short circuit said wire, said circuit being open when said contact is in the other extreme position.

7. An intermittent switch comprising a mount, a pair of spaced fixed contacts, a contact carry ing arm of resilient material having a contact at one end thereof and fixed at its free end to said mount, said mount having a resilient pivot arm, a resilient switch arm affixed at one end to the contact carrying end of said contact arm and having its free end pivotally mounted at the end of said pivot arm, said pivot arm being biased normally to move outwardly from said contact arm and to move the contact into engagement with one of said fixed contacts, said contact arm, said switch arm and said pivot arm being constructed and arranged to alford a position of unstable equilibrium when the end of the pivot arm and said contact arm are in the same plane, a lever extending outwardly from said pivot arm,

a heat extensible wire fixed to the end of said lever to urge said pivot arm inwardly upon cooling and contraction of said wire past' said posi tion of unstable equilibrium for snapping of said contact into engagement with the othery of said fixed contacts, whereby upon expansion of said wire upon heating thereof, said pivot arms will be released to move said switch arm past the position of unstable equilibrium and said switch arm will then snap said contact back into engagement with said first xed contact, said contact when engaging said other xed contact closing a circuit to short circuit said wire, said circuit being open when said contact engages said rst fixed contact.

8. An intermittent switch comprising a substantially rectangular resilient member having bowed portions defining contact arms extending longitudinally inward from the ends thereof and having a pair of narrow heat extensible lateral strips integral therewith on each side of said contact arms, a post of insulating material, means xing the adjacent inner ends of said contact arms to said post, a contact carried by each of said contactarme, a pair of spaced contacts associated with each of the contacts on said contact arms on each side thereof, one of the contacts of each of said pair being engaged by the associated contact on said contact arm when said strips are cool and contracted, said contact arms and said lateral strips being constructed and arranged to afford a position of unstable equilibrium for said contact arms when the lateral strips lie in the same plane as the iixed ends of said contact arms, whereby upon expansion of said lateral strips upon heating thereof and lateral movement thereof with respect to said contact arms, the contacts thereon will remain fixed until the position of unstable equilibruim has been passed by said strips to snap said contacts into engagement with the other of said spaced contacts, said contacts when engaging said last named pair of spaced contacts closing a circuit to short circuit said strips, said circuit being open when said contacts are engaging the rst pair of spaced contacts.

9. The combination set forth in claim 1 in which said contact arm is a substantially rectangular strip of resilient spring metal and said switch arm is also a substantially rectangular strip of resilient spring metal, said Contact arm being conformed to have a central opening of substantially the length of the switch arm, one end of the switch arm being integral with said contact arm at one end of said central opening therein and extending the length thereof, and said resilient means comprises a bowed spring member having one end positioned against the end of the contact arm adjacent the end of the central opening remote from the end to which the switch arm is mounted and the other end against the switch arm adjacent its free end.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,959,205 Hanel May 15, 1934 2,272,021 Riche Feb. 3, 1942 2,312,974 Owens Mar. 2, 1943 2,321,049 Schmidinger June 8, 1943 2,425,717 Bean Aug. 19, 1947 2,508,637 Boiesky May 23, 1950 2,568,476 Weirich et al Sept. 18, 1951 

